Chad, On 1/30/07 6:13 AM, "Chad Wagner" <chad.wagner@xxxxxxxxx> wrote: > Sounds like an opportunity to implement a "Sort Unique" (sort of like a hash, > I guess), there is no need to push 3M rows through a sort algorithm to only > shave it down to 1848 unique records. > > I am assuming this optimization just isn't implemented in PostgreSQL? Not that it helps Igor, but we've implemented single pass sort/unique, grouping and limit optimizations and it speeds things up to a single seqscan over the data, from 2-5 times faster than a typical external sort. I can't think of a way that indexing would help this situation given the required visibility check of each tuple. - Luke
